1. Field of the Invention
The present invention relates to a conductive rubber member. More particularly, the present invention relates to a conductive rubber member suitable as a cleaning member for removing toner which has adhered to a photoreceptor and other members of an image-forming apparatus with which the toner contacts.
2. Description of the Related Art
In image-forming apparatus, researches is being widely conducted to realize a high-speed operation and to form a high-quality image and a high-quality color image. Investigations are being made to enable the image-forming apparatus to achieve such performances by improving the quality of toner. It has been revealed that the image-forming apparatus is capable of achieving the above-described performances by reducing the diameter of the toner from 10 μm, conventionally, adopted to as small as 5 μm. Thus research for reducing the diameter of the toner is being conducted energetically and widely.
However, toner having a small diameter of 5 μm is liable to readily adhere to itself. In addition, it is difficult to remove the toner that has adhered to a member such as a photoreceptor of an image-forming apparatus. An external additive is added to the toner to prevent it from adhering to itself. However, not only the toner but also the external additive adheres to the photoreceptor and other members of the image-forming apparatus. The most serious problem in the image-forming apparatus is the adhesion of the toner and the external additive to the photoreceptor and other members with which the toner contacts, as described above.
The toner and the external additive are electrostatically transported from a developing roller to the photoreceptor of the image-forming apparatus. The toner and the external additive are transported from the photoreceptor to paper or an intermediate medium in a transfer process. In the transfer process, the toner and the external additive are not completely transferred from the photoreceptor to the paper or the intermediate medium, but actually a part of the toner and the external additive remain adhered to the photoreceptor. Thus it is necessary to perform a cleaning process. However, when the diameter of the toner is as small as 5 μm, it is very difficult to completely remove the toner and the external additive from the photoreceptor in the cleaning process. Consequently in a charging process to be performed after the cleaning process, a conductive member such as a charging roller is stained by the toner and the external additive which have not been completely removed in the cleaning process. Consequently defective charging occurs or the conductive member is damaged, which gives rise to a serious influence on the reliability of the image-forming apparatus.
A blade is used widely in the cleaning process to scrape the toner and the external additive from the surface of the photoreceptor and the like. The scraped toner and external additive are collected to a toner collection box. This mechanism necessitates the image-forming apparatus to be provided with a complicated mechanism for transporting the scraped toner and external additive to the toner collection box. As such it is difficult to recycle the toner. In this mechanism, because a cleaning operation is performed with only the blade, it is necessary to scrape the toner and the external additive by applying a very high pressure thereto. This causes the toner to deteriorate to a large extent. Even though the toner can be recycled in this mechanism, the toner is incapable of maintaining sufficient chargeability.
In the image-forming apparatus, there is a demand for a higher-speed operation and higher-quality image and color image, improvement in reliability and, in addition, energy-saving by recycling or reusing the toner. In compliance with these demands, development of a novel cleaning mechanism and members preventing deterioration of the toner has been urgent.
A roller-charging apparatus was proposed as a cleaning mechanism to comply with the above-described demand, as disclosed in Japanese Patent Application Laid-Open No. 6-342237 (patent document 1). The cleaning mechanism includes a contact-type charging roller and a cleaning blade mounted on the charging roller under pressure, for removing foreign substances such as the toner which is adhered to the surface of the charging roller. However, as disclosed in the description of “Examples” in the specification, the surface of the charging roller is coated with a polyamide resin or a fluorocarbon resin. Thus toner which has been collected from the charging roller is not destaticized and may be charged to a greater extent, which necessitates the cleaning blade to be mounted on the charging roller at a higher pressure. Consequently the toner tends to deteriorate. In addition, the coating material formed on the surface of the charging roller becomes worn by repeated use of the charging roller. As a result, the initials, favorable chargeability cannot be maintained and the foreign substance such as the toner is removed at a low efficiency.
The cleaning means is disclosed in Japanese Patent Application Laid-Open No. 2001-209239 (patent document 2). The cleaning means includes an elastic member, having a polarity opposite to that of toner, which is in contact with the charging roller and the magnet proximate to the elastic member and not in contact with the charging roller. In the cleaning means, the toner which has adhered to the charging roller is scraped by the elastic member and collected by the magnet. The cleaning means is effective for removing a magnetic toner from the charging roller but insufficient in removing a nonmagnetic toner and the external additive which have adhered to the charging roller. Consequently the external additive and the unmagnetic toner remain on the charging roller. Thus the cleaning means cannot be reliably used for a long time.
The cleaning apparatus disclosed in Japanese Patent Application Laid-Open No. 2002-82537 (patent document 3) cleans a liquid developer which remains on the intermediate transfer body. The cleaning apparatus is effective for an image-forming apparatus using the liquid developer, but is not nonapplicable to an image-forming apparatus using a dry developer nor has a mechanism in which recycling of the developer is considered.